SimpleIO - TriacOut Design Notes

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DESIGN NOTES

Design Center » TriacOut Design Notes

These are notes from the development of the TriacOut pc boards.

This project came about when trying to locate one for Russ' outdoor sign at Rosy's Jazz Hall, then running into the same issues when setting up Bob's sprinkler system. The former is not completed; the latter was done using opto-22-style modules, and led to developing this board.

The boards that exist are expensive general-purpose PC I/O boards, stage lighting systems, one simple but expensive board for Las Vegas lights, and too-simple hobby kits.

General Specs

Channels: 2, 4, 6, 8, 12 (for an octave), 16 (if it fits). Even 1, just to have a tiny one?
Watts/Channel: at least 150W. Reasonable triacs (400W probably available).

Heat sink easy to attach.
UL standards for general I/O, outdoor signs.
Power – expect DC V, can use a separate transformer or power supply.

Output

At least 150W/channel. Reasonable triacs.
Electrical codes vary whether switching hot or neutral, so stay generic.
Future options: provide heat sink, fuse per channtl, sense output on/off (fuse blown).

Triac

Chose STMicro BTA08-400B, insulated, 8A, 400V, 50mA gate.
Same inexpensive price as 6A.

Originally had STMicro BTA06-400B, insulated, 6A, 400V, 50mA gate.
The 6A and 400V is inexpensive.
400V in Mouser is least expensive, even though it seems to not exist on ST's site. Don't know if the part is new or old.
Mouser is much cheaper than DigiKey for this one.

Insulated because I like the idea, and you can clamp a common heat sink to all of them. I think some people get non-insulated for better thermal transfer.
50mA gate because we don't really need the sensitivity.
Would like snubberless; it means it has the snubber, so your circuit doesn't need it. Meant for inductive loads (probably don't need the MOV)!
The 400V price wins, and doesn't come snubberless.

Power

Expect DC V in. Can use a separate transformer or power supply.
5V in, too far to travel / keep clean. Expect an interface/logic board anyway, for serial-to-parallel. This can provide a 5V regulator.

Fuse

Fast-acting, just from various notes. Both fast and slow aren't really that quick unless it's a real short.
Also, fast-acting is cheaper, so probably more popular.
Littlefuse 217 series is fast-activing, and IEC (and UL) standards.
6.3 A is the highest before the price jumps; it's somewhat arbitrary anyway. Call it 1 A per channel.
Write a design note to increase the fuse if desired.

Input

Optoisolator input, with pull-up resistor.
Supply common DC V (nominally 5V) to pull-up resistors.
Ground individual inputs to turn on.

Zero-crossing optoisolators. MOC3041 handles 110 and 220 VAC (same cost as MOC3031, which is only for 110V use).
copy

Input current/voltage details

Size for 5 V min supply to the optos.
Used 220 ohm resistors, as a nominal 5V/15mA.
Forward voltage on opto is 1.2V, so (5 – 1.2) / 15 mA = 250 ohm, round to standard 220 ohm.
For the max voltage, the 1/4W resistor will be the limit. V^2 / 220 ohm = 0.25 W, so V = 7.4 V max. 9 V would have been nice, and probably would be ok, running the resistors hot, but preferred to be able to have 5 V work.

Expect DC V in. Can use a separate transformer or power supply.
Expect an interface/logic board anyway, for serial-to-parallel. This can provide a 5V regulator if running a higher voltage for the distance to the field.

Layout

Split the layout notes out to the TriacOut Board Notes.

Misc

Thru-hole for hobbyist rework. Connectors etc. will probably set the board size anyway.
The Las Vegas board has sockets for triacs, so they must blow fairly often. Sockets are probably a pain for assembly, even if convenient in the field.
Wanted 2-piece plug connectors, to unplug wiring, rather than just screw terminals. Nice, but too expensive. Did find some for the TriacOut8 board Rev B.
2 pins/channel, even if one is common to all channels, just for wiring.
Wanted prototype area, as a strip down the board for all channels. No room on this small board. Could do this on the logic boards.
Optional MOV footprint for inductive loads.